Aminoferrocene derivative and tandem organic light-emitting diode containing the same

ABSTRACT

An aminoferrocene derivative is represented by the formula (I): 
     
       
         
         
             
             
         
       
         
         
           
             wherein Ar 1  and Ar 2  independently represent a substituted or unsubstituted C 6 -C 10  aryl group. The aminoferrocene derivative is useful for forming a p-type carrier generation layer of a tandem OLED so that the tandem OLED has superior luminous efficiencies in terms of maximum luminance, maximum external quantum efficiency, maximum current efficiency, etc.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of Taiwanese Application No. 104121302,filed on Jul. 1, 2015.

FIELD

This disclosure relates to an aminoferrocene derivative and a tandemorganic light-emitting diode including the aminoferrocene derivative.

BACKGROUND

Organic light-emitting diodes (referred to as OLEDs hereinafter) haveadvantages such as self-emission, high contrast, high luminance, wideviewing angle and fast response, and thus have been widely used indisplays. As compared to a conventional single OLED unit, a tandem OLED,which consists of two or more OLED units connected in series, mayachieve the same luminance as that of the conventional single OLED unitat a relatively low current density, and thus has a relatively longservice life. In addition, the colors of lights emitted by therespective OLED units of the tandem OLED may be adjusted individually,and thus the tandem OLED is suitable for emitting white light.

The tandem OLED includes a p-type carrier generation layer forgenerating holes. It is disclosed, for example, in J. Mater. Chem.,2011, 21, pp. 15332-15336, that a thiophene derivative is used forforming the p-type carrier generation layer of the tandem OLED. However,few literature has discussed in detail materials that can serve as thep-type carrier generation layer of the tandem OLED and how suchmaterials can be used to modify the luminance, the external quantumefficiency, the current efficiency and the like of the tandem OLED.

Therefore, there is still a need in the art to develop a novel compoundfor the p-type carrier generation layer of the tandem OLED in order toenhance the luminance, the external quantum efficiency, the currentefficiency and the like of the tandem OLED as compared to theconventional single OLED unit.

SUMMARY

A first object of this disclosure is to provide an aminoferrocenederivative for a p-type carrier generation layer of a tandem OLED so asto enhance the luminance, the external quantum efficiency, the currentefficiency and the like of the tandem OLED as compared to a conventionalsingle OLED unit.

A second object of this disclosure is to provide a tandem organiclight-emitting diode which includes a p-type carrier generation layerformed from the aminoferrocene derivative.

According to a first aspect of this disclosure, there is provided anaminoferrocene derivative represented by formula (I):

wherein

Ar¹ and Ar² independently represent a substituted or unsubstitutedC₆-C₁₀ aryl group.

According to a second aspect of this disclosure, there is provided atandem organic light-emitting diode which includes a p-type carriergeneration layer formed from the aminoferrocene derivative.

The effect of this disclosure resides in that the molecular weight andthe thermal stability of the aminoferrocene derivative of thisdisclosure is enhanced by the electron-donating group of —NAr₁Ar₂contained therein so that the aminoferrocene derivative has a relativelyhigh HOMO level as compared to that of conventional organicsemiconductor materials. Therefore, the aminoferrocene derivative ofthis disclosure may be used for forming a p-type carrier generationlayer of a tandem OLED so that the tandem OLED has enhanced luminance,external quantum efficiency, current efficiency and the like as comparedto a conventional single OLED unit.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of this disclosure will become apparent inthe following detailed description of the embodiments with reference tothe accompanying drawings, of which:

FIG. 1 is a schematic sectional view of a tandem OLED of ApplicationExample 1 according to this disclosure;

FIG. 2 is a schematic sectional view of a tandem OLED of ApplicationExample 5 according to this disclosure;

FIG. 3 is a schematic sectional view of an OLED unit of ComparativeApplication Example 1; and

FIG. 4 is a schematic sectional view of an OLED unit of ComparativeApplication Example 3.

DETAILED DESCRIPTION

Aminoferrocene Derivative:

An aminoferrocene derivative according to this disclosure is representedby formula (I):

wherein

Ar¹ and Ar² independently represent a substituted or unsubstitutedC₆-C₁₀ aryl group.

Preferably, Ar¹ and Ar² independently represent a substituted orunsubstituted phenyl.

More preferably, Ar¹ and Ar² independently represent a para-substitutedor unsubstituted phenyl.

More preferably, Ar¹ and Ar² independently represent a phenyl groupsubstituted with at least one (preferably one) substituent selected fromthe group consisting of a substituted or unsubstituted C₁-C₇ alkylgroup, an unsubstituted phenyl group, a diphenylamino-substituted phenylgroup, and a ferrocenyl group. Preferably, the substituent includes anunsubstituted C₁-C₇ alkyl group and a substituted or unsubstitutedphenyl. More preferably, the substituent includes a methyl group, anunsubstituted phenyl, and a phenyl group substituted with adiphenylamino group.

Examples of the aminoferrocene derivative illustrated in followingexamples include compounds Fc01, Fc02, Fc03, and Fc04:

wherein Ph represents a phenyl group.Production of Aminoferrocene Derivative:

The aminoferrocene derivative of this disclosure is produced bysubjecting an aminoferrocene compound and a halo-substituted aromaticcompound to a reaction in the presence of a catalyst, a solvent and abase.

The halo-substituted aromatic compound used in the following illustratedexamples includes 4-bromobiphenyl, 4-iodotoluene, and4′-bromo-N,N-diphenylbiphenyl-4-amine.

Preferably, the catalyst is a palladium catalyst, which is formed from apalladium compound and a ligand.

In the following illustrated examples, the palladium compound ispalladium acetate (Pd(OAc)₂) or bis(dibenzylideneacetone)palladium(Pd(dba)₂), and the ligand is 1,1′-bis(diphenylphosphio)ferrocene(dppf), 2-dicyclohexylphosphino-2′,6′-di-Isopropoxybiphenyl (RuPhos), ortributyl-phosphine.

The solvent used in the following illustrated examples is toluene.

The base used in the following illustrated examples is sodiumtert-butoxide (NaO^(t)Bu).

The following examples are provided to illustrate the embodiments of thedisclosure, and should not be construed as limiting the scope of thedisclosure.

Preparation Example 1 Preparation of Aminoferrocene

Under a nitrogen atmosphere, ferrocene (10 g, 53.8 mmol) was dissolvedin anhydrous n-hexane (50 ml), followed by adding and mixing withtetramethylethylenediamine (TMEDA, 18.1 ml, 84.5 mmol) A solution ofn-butyllithium (n-BuLi) in n-hexane (2.5 M, 48.0 ml) was added slowlydropwise at 0° C., followed by stirring at 25° C. After stirring for 12hours and removing the solvent, a light orange yellow complex wasformed. The complex was added to anhydrous ethyl ether (200 ml),followed by stirring to disperse the complex in anhydrous ethyl etherand lowering the temperature of the dispersion to −78° C. A solution ofiodine (19.0 g) in ethyl ether (350 ml) was added to the dispersionslowly dropwise, and the temperature was raised to 25° C. After stirringfor a further hour, the reaction was poured into an aqueous ferricchloride (FeCl₃) solution (5 wt %, 100 ml), followed by extraction withethyl ether (200 ml). An organic layer thus obtained was washed tentimes with an aqueous ferric chloride (FeCl₃) solution (5 wt %, 100 ml)and then was washed with water until the aqueous layer was clear.Thereafter, water was removed using anhydrous MgSO₄ and solvent was alsoremoved to obtain a mixture in the form of a blackish brown liquid ofcompound a and compound b as shown in scheme I in a molar ratio of 1:1.

The obtained mixture (2.5 g, 6.67 mmol), cuprous iodide (CuI, 128 mg,0.67 mmol), ferric chloride (FeCl₃, 107 mg, 0.67 mmol), sodium hydroxide(NaOH, 540 mg, 13.3 mmol), aqueous ammonia (15 M, 30 ml), and ethanol(EtOH, 30 ml) were placed in a high pressure reaction tube of 150 ml. Areaction was conducted at 90° C. for 12 hours. After the temperature ofthe content in the reaction dropped to 25° C., ethyl ether (200 ml) wasadded and the content in the reaction tube was washed three times withan aqueous sodium hydroxide solution (1.0 M, 150 ml). Then, water wasremoved using anhydrous MgSO₄ and solvent was also removed to obtain anorange brown crude product, which was purified by column chromatography(eluent: ethyl acetate/n-hexane=1/2 (v/v)) to obtain aminoferrocenecompound c shown in Scheme I in the form of a yellowish brown solid(yield: 48%).

¹H NMR (400 MHz, CDCl₃) of aminoferrocene compound c: δ 4.08 (s, 5H),3.97 (t, J=1.6, 2H), 3.82 (t, J=1.6, 2H), 2.58 (br, 2H).

Example 1 Preparation of Aminoferrocene Derivative (Fc01)

Preparation of Compound BPAFc:

The aminoferrocene compound (300 mg, 1.49 mmol) obtained in PreparationExample 1, 4-bromobiphenyl (380 mg, 1.64 mmol), palladium acetate(Pd(OAc)₂, 17 mg, 0.075 mmol), 1,1′-bis(diphenylphosphino)ferrocene(dppf, 67 mg, 0.12 mmol), and sodium tert-butoxide (NaO^(t)Bu, 577 mg, 6mmol) were mixed in toluene (5 ml, as a solvent). A reaction wasconducted at 90° C. for 72 hours. The reaction was poured into purewater and was extracted five times with ethyl ether (60 ml). The organiclayer thus obtained was dried using anhydrous magnesium sulfate. Afterthe solvent was removed, purification was conducted by columnchromatography (eluent: n-butane/ethyl acetate=3/2 (v/v)) to obtaincompound BPAFc in the form of an orange solid (yield: 68%). Thestructure of compound BPAFc is shown in Scheme II.

Preparation of Compound Fc01:

Compound BPAFc (100 mg, 0.283 mmol) thus obtained, 4-iodotoluene (123mg, 0.566 mmol), bis(dibenzylideneacetone)palladium (Pd(dba)₂, 4 mg,0.007 mmol), 2-dicyclohexylphosphino-2′,6′-diisopropoxybiphenyl (RuPhos,7 mg, 0.015 mmol), and sodium tert-butoxide (NaO^(t)Bu, 109 mg, 1.13mmol) were mixed in toluene (3 ml, as a solvent). A reaction wasconducted at 130° C. for 72 hours. Pd(dba)₂ was filtered usingdiatomaceous earth and silica gel. The reaction was washed using ethylacetate and the solvent was removed. Purification was conducted bycolumn chromatography (eluent: n-hexane/ethyl acetate=3/1 (v/v)),followed by sublimation (two times) to obtain compound Fc01 in the formof an orange red solid (yield: 80%).

Analysis for compound BPAFC: ¹H NMR (400 MHz, CDCl₃): δ 7.54 (d, J=8.0Hz, 2H), 7.45 (d, J=8.8 Hz, 2H), 7.38 (t, J=8.0 Hz, 2H), 7.25 (t, J=7.6Hz, 1H), 6.95 (d, J=8.8 Hz, 2H), 4.99 (br, 1H), 4.27 (s, 2H), 4.20 (s,5H), 4.05 (s, 2H); ¹³C NMR (100 MHz. CDCl₃): δ 141.0, 131.8, 128.9,128.7, 127.7, 126.9, 126.4, 126.3, 114.9, 68.9, 64.6 and 62.0; HRMS(EI⁺, m/z) calculated for C₂₂H₁₉NFe: 353.0867. found: 353.0869.

Analysis for compound Fc01: ¹H NMR (400 MHz. CDCl₃): δ 7.55 (dd, J=8.0,0.8 Hz, 2H), 7.47 (dd, J=8.0, 2.0 Hz, 2H), 7.37 (t, J=8.0 Hz, 2H),7.30-7.23 (m, 3H), 7.21 (q, J=6.0 Hz, 4H), 4.15 (s, 5H), 4.30 (t, J=1.6,2H), 4.10 (t, J=2.0, 2H), 2.36 (s, 3H); ¹³C NMR (100 MHz. CDCl₃): δ147.2, 144.6, 140.8, 134.2, 133.8, 130.0, 128.7, 127.4, 126.7, 126.6,121.8, 106.9, 68.9, 63.9, 60.1 and 21.0; HRMS (EI⁺, m/z) calculated forC₂₉H₂₅NFe: 443.1336. found: 443.1339.

Preparation Example 2 Preparation of Aminoferrocene Derivative (Fc02)

Preparation of Compound DPABPAFc:

The aminoferrocene compound (300 mg, 1.5 mmol) obtained in PreparationExample 1,4′-bromo-N,N-diphenylbiphenyl-4-amine (1.8 g, 4.5 mmol),palladium acetate (Pd(OAc)₂, 17 mg, 0.075 mmol), a solution oftributylphosphine in n-hexane (0.1 ml, 10 wt %), and sodiumtert-butoxide (NaOtBu, 1.13 g, 11.8 mmol) were mixed in toluene (6 ml,as a solvent). A reaction was conducted at 130° C. for 72 hours.Pd(dba)₂ was filtered using diatomaceous earth and silica gel. Thereaction was washed using ethyl acetate and the solvent was removed.Purification was conducted by column chromatography (eluent:n-hexane/ethyl acetate in a gradient from 4/1 to 3/2 (v/v)) to obtaincompound DPABPAFc (yield: 50%). The structure of compound DPABPAFc isshown in scheme III.

Preparation of Compound Fc02:

Compound Fc02 was prepared by a process similar to that for preparingcompound DPABPAFc except that the amount of4′-bromo-N,N-diphenylbiphenyl-4-amine was 7.90 g (19.7 mmol) and thatsublimation (two times) was conducted after column chromatography.Compound Fc02 was obtained in the formed of a red solid (yield: 40%).

Analysis for compound DPABPAFc: ¹H NMR (400 MHz. CDCl₃): δ 7.42 (t,J=8.0 Hz, 4H), 7.24 (t, J=8.0 Hz, 4H), 7.11 (d, J=8.0 Hz, 4H), 7.00 (t,J=7.2 Hz, 2H), 6.92 (d, J=7.6 Hz, 2H), 4.89 (br, 1H), 4.29 (s, 2H), 4.21(s, 5H), 4.08 (s, 2H); ¹³C NMR (100 MHz. CDCl₃): δ 147.8, 146.2, 141.9,135.3, 131.2, 129.2, 127.2, 127.0, 124.4, 124.1, 122.6, 115.1, 69.0,64.7, and 61.8; HRMS (EI⁺, m/z) calculated for C₃₄H₂₈N2Fe: 520.1602.found: 520.1599.

Analysis for compound Fc02: ¹H NMR (400 MHz. CDCl₃): δ 7.52 (d, J=8.4Hz, 4H), 7.46 (d, J=8.8 Hz, 4H), 7.33 (d, J=8.4 Hz, 4H), 7.27-7.23 (m,8H), 7.11 (d, J=8.4 Hz, 8H), 7.02 (d, J=8.0 Hz, 4H), 4.17 (s, 5H), 4.11(s, 2H), 4.04 (s, 2H); ¹³C NMR (100 MHz. CDCl₃): δ 147.7, 147.7, 146.5,141.9, 135.0, 129.2, 127.5, 127.4, 127.2, 124.5, 124.3, 124.2, 124.0,122.8, 122.7, 118.0, 69.0, 64.0, and 60.4; HRMS (FAB⁺, m/z) calculatedfor C₅₈H₄₆N3Fe: 840.3041. found: 840.3044.

Example 3 Preparation of Aminoferrocene Derivative (Fc03)

The process for preparing compound Fc01 in Example 1 was repeated exceptthat compound BPAFc was replaced with compound DPABPAFc (132 mg, 0.283mmol) obtained in Example 2 and that n-hexane/ethyl acetate in agradient from 3/1 to 1/1 (v/v) was used as eluent in the purificationprocess via column chromatography which was followed by sublimation (twotimes). Compound Fc03 was obtained in the form of an orange red solid(yield: 55%).

Analysis for compound Fc03: ¹H NMR (400 MHz. CDCl₃): δ 7.43 (t, J=8.0Hz, 4H), 7.26-7.16 (m, 8H), 7.11-7.02 (m, 5H), 7.00 (t, J=7.6 Hz, 2H),4.15 (s, 5H), 4.01 (s, 2H), 4.00 (s, 2H), 2.35 (s, 3H); ¹³C NMR (100MHz. CDCl₃): δ 147.7, 146.8, 146.5, 134.9, 134.0, 133.6, 129.9, 129.4,129.2, 127.2, 126.9, 126.8, 126.4, 124.2, 124.1, 122.7, 122.3, 68.8,63.8, 60.0, and 21.0.

Example 4 Preparation of Aminoferrocene Derivative (Fc04

The process for preparing compound BPAFc in Example 1 was repeatedexcept that 4-bromopiphenyl was used in an amount of 840 mg (3.61 mmol)and that n-hexane/ethyl acetate in a ratio of 3/1 (v/v) was used aseluent in the purification process via column chromatography which wasfollowed by sublimation (two times). Compound Fc04 was obtained in theform of a red solid (yield: 42%).

Analysis for compound Fc04: ¹H NMR (400 MHz. CDCl₃): δ 7.60-7.55 (m,8H), 7.42 (t, J=8.0 Hz, 4H), 7.34 (d, J=8.4 Hz, 4H), 7.31 (t, J=7.6 Hz,2H), 4.18 (s, 5H), 4.10 (s, 2H), 4.05 (s, 2H); ¹³C NMR (100 MHz. CDCl₃):δ 146.8, 140.6, 135.7, 128.8, 127.7, 126.9, 126.8, 124.5, 69.0, 64.0,and 60.5.

Measurement of HOMO and LUMO Level Values for Compounds Fc01, Fc02, Fc03and Fc04:

HOMO and LUMO level values for each of compounds Fc01, Fc02, Fc03 andFc04 obtained in Examples 1-4 was measured using a cyclic voltammeter(CH Instruments), a photoelectron spectroscope (AC-2) and an ultravioletphotoelectron spectroscope (NSRRC beamline 24A1). The results are shownin Table 1.

TABLE 1 Fc01 Fc02 Fc03 Fc04 LUMO/HOMO 2.0/4.4 2.1/4.4 2.1/4.4 2.1/4.4(eV/eV) by CV LUMO/HOMO 2.7/5.1 3.0/5.3 2.8/5.1 2.9/5.2 (eV/eV) by AC-2LUMO/HOMO 3.0/5.4 2.9/5.2 2.8/5.1 3.0/5.3 (eV/eV) by UPS

Application Example 1

A tandem OLED having structure I was manufactured in which a p-typecarrier generation layer was formed from compound Fc03.

Structure I:

ITO(150)/NPB(50)/TCTA:4 wt%Ir(piq)₃(30)/BPhen(20)/BPhen:6wt%LiF(5)/Al(1)/C₆₀(4)/Fc03(1)/MoO₃(1)/NPB(50)/TCTA:4wt%Ir(ppy)₃(30)/BPhen(20)/LiF(1)/Al (100)

The numerical values in brackets indicate thicknesses (nm) of the layersin structure I. Structure I was also schematically illustrated inFIG. 1. The elements denoted by the reference numbers 1-14 in FIG. 1 areset forth in Table 2 below. The materials and thicknesses of the layersshown in FIG. 1 are also indicated in Table 2.

TABLE 2 Ref. Thickness Nos. Materials (nm)  1 Anode ITO 150  2 Holetransport NPB 50 layer  3 Emissive layer TCTA doped with 30 4 wt %Ir(piq)₃  4 Electron BPhen 20 transport layer  5 Electron BPhen dopedwith 5 injection layer 6 wt % LiF  6 Electron Al 1 injection layer  7n-type carrier C₆₀ 4 generation layer  8 p-type carrier Compound Fc03 1generation layer (Example 3)  9 Hole injection MoO₃ 1 layer 10 Holetransport NPB 50 layer 11 Emissive layer TCTA doped with 30 4 wt %Ir(ppy)₃ 12 Electron BPhen 20 transport layer 13 Cathode LiF 1 14Cathode Al 100

The abbreviations for the materials indicated in Table 2 are explainedas follows.

-   ITO: indium tin oxide;-   NPB:    N,N′-bisphenyl-N,N′-bis(1-naphthalenyl)-1,1′-biphenyl-4,4′-diamine];-   TCTA: tris(4-carbazoyl-9-yl-phenyl)amine]

-   Ir(piq)₃: tris(1-phenyl-isoquinoline)iridium(III)];

-   BPhen: 4,7-diphenyl-1,10-phenanthroline);

-   MoO₃: molybdenum trioxide);-   Ir(ppy)₃: tris(2-phenyl-pyridine)iridium(III)].

Application Example 2

A tandem OLED having structure II was manufactured in which a p-typecarrier generation layer was formed from compound Fc03.

Structure II:

ITO(150)/NPB(50)/TCTA:4 wt%Ir(ppy)₃(30)/BPhen(20)/BPhen:6wt%LiF(5)/Al(1)/C₆₆(4)/Fc03(1)/MoO(1)/NPB(50)/TCTA:4wt%Ir(piq)₃(30)/BPhen(20)/LiF(1)/Al (100)

The numerical values in brackets indicate thicknesses (nm) of the layersin structure II. The tandem OLED of Application Example 2 has the samelayer structure as that of the tandem OLED of Application Example 1schematically shown in FIG. 1 except that in Application Example 2, theemissive layer 3 is formed from TCTA doped with 4 wt % Ir(ppy)₃ and theemissive layer 11 is formed from TCTA doped with 4 wt % Ir(pig)₃.

Application Example 3

A tandem OLED having structure III was manufactured in which a p-typecarrier generation layer was formed from compound Fc04.

Structure III:

ITO(150)/NPB(50)/TCTA:4 wt%Ir(ppy)₃ (30)/BPhen(20)/BPhen:6wt%LiF(5)/Al(1)/C₆₀(4)/Fc04(1)/MO₃(1)/NPB(50)/TCTA:4wt%Ir(ppy)₃(30)/BPhen(20)/LiF(1)/Al (100)

The numerical values in brackets indicate thicknesses (nm) of the layersin structure III. The tandem OLED of Application Example 3 has the samelayer structure as that of the tandem OLED of Application Example 1schematically shown in FIG. 1 except that in Application Example 3, theemissive layer 3 is formed from TCTA doped with 4 wt % Ir(ppy)₃ and thep-type carrier generation layer 8 is formed from compound Fc04 preparedin Example 4.

Application Example 4

A tandem OLED having structure IV was manufactured in which a p-typecarrier generation layer was formed from compound Fc04.

Structure IV:

ITO(150)/NPB(50)/TCTA:4 wt%Ir(piq)₃(30)/BPhen(20)/BPhen:6wt%LiF(5)/Al(1)/C₆₀(4)/Fc04(1)/MO₃(1)/NPB(50)/TCTA:4wt%Ir(ppy)₃(30)/BPhen(20)/LiF(1)/Al(100)

The numerical values in brackets indicate thicknesses (nm) of the layersin structure IV. The tandem OLED of Application Example 4 has the samelayer structure as that of the tandem OLED of Application Example 1schematically shown in FIG. 1 except that in Application Example 4, thep-type carrier generation layer 8 is formed from compound Fc04 preparedin Example 4.

Application Example 5

A tandem OLED having structure V was manufactured in which a p-typecarrier generation layer was formed from compound Fc04.

Structure V:

ITO(150)/NPB(30)/TCTA(20)/TCTA:TPBi:8wt%Ir(ppy)₃(30)/TPBi(60)/TPBi:6wt%LiF(5)/Al(1)/C₆₀(4)/Fc04(1)/MoO₃(1)/NPB(30)/TCTA(20)/TCTA:TPBi:8wt%Ir(ppy)₃/TPBi(60)/LiF(1)/Al(100)

The numerical values in brackets indicate thicknesses (nm) of the layersin structure V. Structure V was also schematically illustrated in FIG.2. The elements denoted by the reference numbers 15-30 in FIG. 2 are setforth in Table 3 below. The materials and thicknesses of the layersshown in FIG. 2 are also indicated in Table 3.

TABLE 3 Ref. Thickness Nos. Materials (nm) 15 Anode ITO 150 16 Holetransport NPB 30 layer 17 Hole injection TCTA 20 layer 18 Emissive layerTCTA/TPBi doped 30 with 8 wt % Ir(ppy)₃ 19 Electron TPBi 60 transportlayer 20 Electron TPBi* doped with 5 injection layer 6 wt % LiF 21Electron Al 1 injection layer 22 n-type carrier C₆₀ 4 generation layer23 p-type carrier Compound Fc04 1 generation layer (Example 4) 24 Holeinjection MoO₃ 1 layer 25 Hole transport NPB 30 layer 26 Hole injectionTCTA 20 layer 27 Emissive layer TCTA/TPBi doped 30 with 8 wt % Ir(ppy)₃28 Electron TPBi 60 transport layer 29 Cathode LiF 1 30 cathode Al 100*TPBi: 1,3,5-tris(N-phenylbenzimidizol-2-yl) benzene

Application Example 6

A tandem OLED having structure VI was manufactured in which a p-typecarrier generation layer was formed from compound Fc01.

Structure VI:

ITO(150)/NPB(30)/TCTA(20)/TCTA:TPBi:8wt%Ir(ppy)(30)/TPBi(60)/TPBi:6wt%LiF(5)/Al(1)/C₆₀(4)/Fc01(1)/MoO₃(1)/NPB(30)/TCTA(20)/TCTA:TPBi:8wt%Ir(ppy)₃/TPBi(60)/LiF(1)/Al(100)

The numerical values in brackets indicate thicknesses (nm) of the layersin structure VI. The tandem OLED of Application Example 6 has the samelayer structure as that of the tandem OLED of Application Example 5schematically shown in FIG. 2 except that in Application Example 6, thep-type carrier generation layer 23 is formed from Fc01 prepared inExample 1.

Application Example 7

A tandem OLED having structure VII was manufactured in which a p-typecarrier generation layer was formed from compound Fc03.

Structure VII:

ITO(150)/NPB(30)/TCTA(20)/TCTA:TPBi:8wt%Ir(ppy)₃(30)/TPBi(60)/TPBi:6wt%LiF(5)/Al(1)/C₆₀(4)/Fc03(1)/MoO₃(1)/NPB(30)/TCTA(20)/TCTA:TPBi:8wt%Ir(ppy)₃/TPBi(60)/LiF(1)/Al(100)

The numerical values in brackets indicate thicknesses (nm) of the layersin structure VII. The tandem OLED of Application Example 7 has the samelayer structure as that of the tandem OLED of Application Example 5schematically shown in FIG. 2 except that in Application Example 7, thep-type carrier generation layer 23 is formed from Fc03 prepared inExample 3.

Comparative Application Example 1

An OLED unit having structure VIII was manufactured.

Structure VIII:

ITO(150)/NPB(50)/TCTA:4wt%Ir(piq)₃(30)/BPhen(20)/LiF(1)/Al(100)

The numerical values in brackets indicate thicknesses (nm) of the layersin structure VIII. Structure VIII was also schematically illustrated inFIG. 3. The elements denote by the reference numbers 31-36 in FIG. 3 areset forth in Table 4 below. The materials and thicknesses of the layersshown in FIG. 3 are also indicated in Table 4.

TABLE 4 Ref. Thickness Nos . Materials (nm) 31 Anode ITO 150 32 Hole NPB50 transport layer 33 Emissive TCTA doped 30 layer with 4 wt % Ir(piq)₃34 Electron BPhen 20 transport layer 35 Cathode LiF 1 36 Cathode Al 100

Comparative Application Example 2

An OLED unit having structure IX was manufactured.

Structure IX:

ITO(150)/NPB(50)/TCTA:4wt%Ir(ppy)₃(30)/BPhen(20)/LiF(1)/Al(100)

The numerical values in brackets indicate thicknesses (nm) of the layersin structure IX. The OLED unit of Comparative Application Example 2 hasthe same layer structure as that of the OLED unit of ComparativeApplication Example 1 schematically shown in FIG. 3 except that inComparative Application Example 2, the emissive layer 33 is formed fromTCTA doped with 4 wt % Ir(ppy)₃.

Comparative Application Example 3

An OLED unit having structure X was manufactured.

Structure X:

ITO(150)/NPB(30)/TCTA(20)/TCTA:TPBi:8wt%Ir(ppy)₃(30)/TPBi(60)/TPBi:6wt%LiF(5)/Al(100)

The numerical values in brackets indicate thicknesses (nm) of the layersin structure X. Structure X was also schematically illustrated in FIG.4. The elements denoted by the reference numbers 37-43 in FIG. 4 are setforth in Table 5 below. The materials and thicknesses of the layersshown in FIG. 4 are also indicated in Table 5.

TABLE 5 Ref. Thickness Nos . Materials (nm) 37 Anode ITO 150 38 Hole NPB30 transport layer 39 Hole TCTA 20 injection layer 40 Emissive TCTA/TPBilayer doped with 30 8 wt % Ir(ppy)₃ 41 Electron TPBi 60 transport layer42 Electron TPBi doped 5 injection with 6 wt % LiF layer 43 cathode Al100

Comparative Application Example 4

An OLED unit having structure XI was manufactured.

Structure XI:

ITO(150)/NPB(30)/TCTA(20)/TCTA:TPBi:8wt%Ir(ppy)₃(30)/TPBi(60)/LiF(1)/Al(100)

The numerical values in brackets indicate thicknesses (nm) of the layersin structure XI. The OLED unit of Comparative Application Example 4 hasthe same layer structure as that of the OLED unit of ComparativeApplication Example 3 schematically shown in FIG. 4 except that inComparative Application Example 4, the electron injection layer 4 isformed from LiF and has a thickness of 1 nm.

Analysis of HOMO and LUMO Level Values for Application Examples 1-7:

HOMO and LUMO level values for the materials of the layers in each ofthe tandem OLEDs of Application Examples 1-7 was measured using anultraviolet photoelectron spectroscope. The results for ApplicationExamples 1-4 are shown in Table 6 below and the results for ApplicationExamples 5-7 are shown in Table 7 below.

TABLE 6 HOMO LUMO Materials (eV) (eV) ITO 4.7 — NPB 5.4 2.3 TCTA dopedwith 5.2 3.2 4 wt % Ir(piq)₃ [5.7] [2.4] [TCTA doped with 5.3 2.9 4 wt %Ir(ppy)₃] [5.7] [2.4] BPhen 6.5 3.0 BPhen doped with 6.5 3.0 6 wt % LiFAl — 4.1 C₆₀ 6.2 4.5 Compound Fc03 5.1 2.8 [Compound Fc04] [5.3] [3.0]MoO₃ 5.3 2.3 NPB 5.4 2.3 TCTA doped with 5.3 2.9 4 wt % Ir(ppy)₃ [5.7][2.4] [TCTA doped with 5.2 3.2 4 wt % Ir(piq)₃] [5.7] [2.4] BPhen 6.53.0 LiF — 3.2 Al — 3.2

TABLE 7 HOMO LUMO Materials (eV) (eV) ITO 4.7 — NPB 5.4 2.3 TCTA 5.7 2.4TCTA/TPBi doped with 5.6 3.0 8 wt % Ir(ppy)₃ TPBi 6.2 2.7 TPBi dopedwith 6 wt % LiF 6.2 2.7 Al — 4.1 C₆₀ 6.2 4.5 Compound Fc0 4 5.3 3.0[Compound Fc01] [5.4] [3.0] [Compound Fc03] [5.1] [2.8] MoO3 5.3 2.3 NPB5.4 2.3 TCTA 5.7 2.4 TCTA/TPBi doped with 5.6 3.0 8 wt % Ir(ppy)₃ TPBi6.2 2.7 LiF — 3.2 Al — 3.2

As shown in Table 6, the HOMO level values of compound FC03 (Example 3)and compound Fc04 (Example 4) used for the p-type carrier generationlayer 8 are respectively 5.1 eV and 5.3 eV, which are close or identicalto the HOMO level value (5.3 eV) of MoO₃ used for the hole injectionlayer 9 adjacent to the p-type carrier generation layer 8. Likewise, theLUMO level values of compound FC03 and compound Fc04 used for the p-typecarrier generation layer 8 are respectively 2.8 eV and 3.0 eV, which areclose to the LUMO level value (2.3 eV) of MoO₃ used for the holeinjection layer 9 adjacent to the p-type carrier generation layer 8.

In addition, as shown in Table 7, the HOMO level values of compound Fc04(Example 4), Fc01 (Example 1) and compound Fc03 (Example 3) used for thep-type carrier generation layer 23 are respectively 5.3 eV, 5.4 eV and5.3 eV, which are close or identical to the HOMO level value (5.3 eV) ofMoO₃ used for the hole injection layer 24 adjacent to the p-type carriergeneration layer 23. Likewise, the LUMO level values of compound FC04,compound FC01 and compound Fc03 for the p-type carrier generation layer23 are respectively 3.0 eV, 3.0 eV and 2.8 eV, which are close to theLUMO level value (2.3 eV) of MoO₃ used for the hole injection layer 24adjacent to the p-type carrier generation layer 23.

It has thus been demonstrated that compounds Fc01, Fc03 and Fc04, whichare examples of the aminoferrocene derivative of this disclosure, areuseful as material for forming a p-type carrier generation layer of atandem OLED.

Measurement of Luminous Efficiencies of the tandem OLEDs of ApplicationExamples 1-4 and the OLED Units of Comparative Application Examples 1and 2:

The tandem OLEDs of Application Examples 1-4 and the OLED units ofComparative Application Examples 1 and 2 were tested to obtain luminousefficiencies including driving voltage (V_(d)), maximum luminance (L),maximum external quantum efficiency (η_(ext)), maximum currentefficiency (η_(C)), maximum power efficiency (η_(p)), maximum emissionwavelength (λ_(em)), and CIE coordinates. The results are shown in Table8. The driving voltage (V_(d)), the maximum luminance (L), the maximumexternal quantum efficiency (η_(ext)), the maximum current efficiency(η_(c)) and the maximum power efficiency (η_(p)) were obtained using anoptical meter (Newport 1835-C) and a source measurement unit (Keithley2400 Source Meter®) equipped with a silicon photodiode (Newport 818-ST).The maximum emission wavelength (λ_(em)) was obtained using a HitachiF-4500 fluorescence spectrophotometer.

TABLE 8 Comp. Comp. Appln. Appln. Appln. Appln. Appln. Appln. Ex. 1 Ex.2 Ex. 3 Exm. 4 Ex. 1 Ex. 2 V_(d) (V) 4.51 4.82 4.51 4.52 2.22 2.07L(cd/m²) 126471 76565 90927 110958 43280 59287 [voltage (V)] [15.0][15.5] [15.5] [16.0] [12.5] [11.5] η_(ext) (%) 27.44 14.22 19.73 26.446.28 10.00 [voltage (V)] [5.0] [7.0] [5.5] [5.0] [2.5] [3.0] η_(c)(cd/A) 118.85 60.10 74.71 89.80 19.68 37.88 [voltage (V)] [5.0] [7.0][5.5] [5.0] [2.5] [3.0] η_(p) (Im/W) 74.56 33.21 46.24 56.31 24.63 39.57[voltage (V)] [5.0] [5.5] [5.0] [5.0] [2.5] [3.0] λ_(em) (nm) 513 544514 516 620 514 CIE (0.33, (0.44, (0.29, (0.32, (0.66, (0.26, (x,y)0.59) 0.54) 0.64) 0.60) 0.34) 0.65)

As shown in Table 8, the maximum luminance (L), the maximum externalquantum efficiency (η_(ext)) and the maximum current efficiency (η_(c))of the tandem OLEDs of Application Examples 1-4 which individuallyinclude a p-type carrier generation layer formed from compound Fc03 orcompound Fc04 to serially connect the OLED units of ComparativeApplication Example 1 or 2 are higher than those of the OLED units ofComparative Application Examples 1 and 2. In addition, as shown in theCIE coordinate data in Table 8, the light emitted by the tandem OLEDs ofApplication Examples 1-4 is relatively white as compared to the lightemitted by the OLED units of Comparative Application Examples 1 and 2.It has thus been demonstrated that the aminoferrocene derivative of thisdisclosure is useful as a material for forming a p-type carriergeneration layer of a tandem OLED so that the tandem OLED has superiorluminous efficiencies in terms of maximum luminance (L), maximumexternal quantum efficiency (η_(ext)) and maximum current efficiency(η_(c)) and may emit white light.

The voltage (V), the maximum luminance (L), the maximum external quantumefficiency (η_(ext)), the maximum current efficiency (η_(c)), and themaximum power efficiency (η_(p)) of the tandem OLEDs of ApplicationExamples 1-4 and the OLED units of Comparative Application Examples 1and 2 were tested under the same current density (J). The results areshown in Table 9 below.

TABLE 9 Comp. Comp. Appln. Appln. Appln. Appln. Appln. Appln. Ex. 1 Ex.2 Ex. 3 Ex. 4 Ex. 1 Ex. 2 J 10 10 10 10 10 10 (mA/cm²) V(V) 8.0 8.4 8.18.0 3.7 3.6 L(cd/m²) 10016 5870 6966 7881 1930 3570 η_(ext) (%) 23.1313.89 18.42 22.88 6.17 9.54 η_(c) (cd/A) 100.18 58.74 69.75 78.83 19.3836.14 η_(p) (Im/W) 39.27 21.86 27.14 30.98 16.72 31.32

As shown in Table 9, under the same current density (10 mA/cm²), themaximum luminance (L), the maximum external quantum efficiency(η_(ext)), and the maximum current efficiency (η_(c)) of the tandemOLEDs of Application Examples 1-4 which individually include a p-typecarrier generation layer formed from compound Fc03 or compound Fc04 arehigher than those of the OLED units of Comparative Application Examples1 and 2. It has thus been demonstrated that the aminoferrocenederivative of this disclosure is useful as a material for forming ap-type carrier generation layer of a tandem OLED so that the tandem OLEDhas superior luminous efficiencies in terms of maximum luminance (L),maximum external quantum efficiency (η_(ext)) and maximum currentefficiency (η_(c)).

Measurement of Luminous Efficiencies of the Tandem OLEDs of ApplicationExamples 5-7 and the OLED Units of Comparative Application Examples 3and 4:

The tandem OLEDs of Application Examples 5-7 and the OLEDs ofComparative Application Examples 3 and 4 were tested to obtain luminousefficiencies, including the driving voltage (V_(d)), the maximumluminance (L), the maximum external quantum efficiency (η_(ext)), themaximum current efficiency (η_(c)), the maximum power efficiency(η_(p)), the maximum emission wavelength (λ_(em)), and the CIEcoordinates. The results are shown in Table 10 below.

TABLE 10 Comp. Comp. Appl. Appl. Appl. Appl. Appl. Ex. 5 Ex. 6 Ex. 7 Ex.3 Ex. 4 V_(d)(V) 5.04 5.04 5.07 2.52 2.52 L(cd/m²) 230268 217222 214058196132 223930 [voltage [20.0] [19.5] [20.0] [16.5] [13.5] (V)]η_(ext)(%) 59.51 47.11 48.85 29.08 23.55 [voltage [6.5] [5.5] [5.5][4.0] [6.0] V)] η_(c)(cd/A) 230.45 180.95 187.62 113.05 91.56 [voltage[6.5] [9.5] [5.5] [4.0] [6.0] V)] η_(p)(Im/W) 119.82 80.77 106.95 100.1658.03 [voltage [6.0] [6.5] [5.5] [3.5] [4.5] (V)] λ_(em)(nm) 518 516 516516 516 CIE (0.31, (0.29, (0.31, (0.29, (0.31, (x, y) 0.63) 0.64) 0.63)0.64) 0.63)

As shown in Table 10, the maximum external quantum efficiency (η_(ext))and the maximum current efficiency (η_(c)) of the tandem OLEDs ofApplication Examples 5-7 which individually include a p-type carriergeneration layer formed from compound Fc04, compound Fc01, or compoundFc01 to serially connect the OLED units of Comparative ApplicationExample 3 or 4 are higher than those of the OLED units of ComparativeApplication Examples 3 and 4. It has thus been demonstrated again thatthe aminoferrocene derivative of this disclosure is useful as a materialfor forming a p-type carrier generation layer of a tandem OLED so thatthe tandem OLED has superior luminous efficiencies in terms of maximumexternal quantum efficiency (η_(ext)) and maximum current efficiency(η_(c)).

The voltage (V), the maximum luminance (L), the maximum external quantumefficiency (η_(ext)), the maximum current efficiency (η_(c)), and themaximum power efficiency (η_(p)) of the tandem OLEDs of ApplicationExamples 5-7 and the OLED units of Comparative Application Examples 3and 4 were tested under the same current density (J). The results areshown in Table 11 below.

TABLE 11 Comp. Comp. Appln. Appln. Appln. Appln. Appln. Ex. 5 Ex. 6 Ex.7 Ex. 3 Ex. 4 J 10 10 10 10 10 (mA/cm²) V(V) 12.2 12.6 12.7 6.4 5.4L(cd/m²) 20311 17489 17656 10204 8576 η_(ext)(%) 52.49 45.55 45.99 26.3021.99 η_(c)(cd/A) 203.26 174.97 176.67 102.23 85.51 η_(p)(Im/W) 52.4243.65 43.73 50.21 49.41

As shown in Table 11, under the same current density (10 mA/cm²), themaximum luminance (L), the maximum external quantum efficiency (η_(ext))and the maximum current efficiency (η_(c)) of the tandem OLEDs ofApplication Examples 5-7 which individually include a p-type carriergeneration layer formed from compound Fc04, compound Fc01 or compoundFc03 to serially connect the OLED units of Comparative ApplicationExample 3 or 4 are higher than those of the OLED units of ComparativeApplication Examples 3 and 4. It has thus been demonstrated that theaminoferrocene derivative of this disclosure is useful as a material forforming a p-type carrier generation layer of a tandem OLED so that thetandem OLED has superior luminous efficiencies in terms of maximumluminance (L), maximum external quantum efficiency (η_(ext)) and maximumcurrent efficiency (η_(c)).

In addition, the tandem OLEDs of Application Examples 5-7 and the OLEDunits of Comparative Application Examples 3 and 4 were tested under thesame luminance to obtain the voltage (V), the maximum current density(J), the maximum external quantum efficiency (η_(ext)), the maximumcurrent efficiency (η_(c)), and the maximum power efficiency (η_(p)).The results are shown in Table 12 below.

TABLE 12 Appln. Appln. Appln. Appln. Appln. Ex. 5 Ex. 6 Ex. 7 Ex. 3 Ex.4 L(cd/m²) 100 100 100 100 100 V(V) 6.3 6.8 6.6 3.3 3.2 J 0.043 0.0580.057 0.091 0.427 (mA/cm²) η_(ext)(%) 59.37 44.33 45.36 26.26 4.94η_(c)(cd/A) 229.92 170.26 174.23 102.08 19.22 η_(p)(Im/W) 115.27 78.8182.96 96.09 17.78

As shown in Table 12, under the same luminance (100 cd/m²), the maximumexternal quantum efficiency (η_(ext)) and the maximum current efficiency(η_(c)) of the tandem OLEDs of Application Examples 5-7 which include ap-type carrier generation layer formed from compound Fc04, compound Fc01or compound Fc03 to serially connect the OLED units of ComparativeApplication Example 3 or 4 are higher than those of the OLED units ofComparative Application Examples 3 and 4. It has thus been demonstratedagain that the aminoferrocene derivative of this disclosure is useful asa material for forming a p-type carrier generation layer of a tandemOLED so that the tandem OLED has superior luminous efficiencies in termsof maximum external quantum efficiency (η_(ext)) and maximum currentefficiency (η_(c)). It is also shown in Table 12 that, in terms ofcurrent density required for obtaining the same luminance, the currentdensity of the tandem OLEDs of Application Examples 5-7 is lower thanthose of the OLED units of Comparative Application Examples 3 and 4.

In view of the aforesaid, the aminoferrocene derivative of thisdisclosure is useful as a material for forming a p-type carriergeneration layer to serially connect two or more OLED units to form atandem OLED so that the tandem OLED has superior luminous efficienciesin terms of the maximum luminance, the maximum external quantumefficiency, maximum current efficiency, etc., as compared to therespective OLED units.

While the disclosure has been described in connection with what areconsidered the exemplary embodiment(s), it is understood that thisdisclosure is not limited to the disclosed embodiments but is intendedto cover various arrangements included within the spirit and scope ofthe broadest interpretation so as to encompass all such modificationsand equivalent arrangements.

What is claimed is:
 1. An aminoferrocene derivative represented byformula (I):

wherein Ar¹ and Ar² independently represent a phenyl group substitutedwith at least one substituent selected from the group consisting of anunsubstituted phenyl group, a diphenylamino-substituted phenyl group,and a ferrocenyl group.
 2. The aminoferrocene derivative according toclaim 1, wherein Ar¹ and Ar² independently represent a phenyl which ispara-substituted.
 3. The aminoferrocene derivative according to claim 1,wherein said at least one substituent is a diphenylamino-substitutedphenyl group.
 4. A tandem organic light-emitting diode, comprising ap-type carrier generation layer which includes an aminoferrocenederivative represented by formula (I):

wherein Ar¹ and Ar² independently represent a substituted orunsubstituted C₆-C₁₀ aryl group.